There have been several companies that tried to sell open mobile devices over the years, but people have shown time and time again that they don't want to buy that product. We can wish it were different all we like, but in general we aren't entitled to money-losing, unmarketable products.

A functioning government committed to free markets would mandate unlocked devices.

The unregulated market naturally coalesces into oligopolies or monopolies and doesn’t fix issues like this.